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Wednesday, 24 April 2013

Connected to my Raspberry Pi is a DS18B20 temperature sensor which I have mounted inside the case roughly above the processor. I wanted to map the temperature profile inside the case and have a visual representation of it. To do this I joined up a Python script, an SQLite3 database and LabVIEW.

I only have one temperature sensor connected and the RasPi doesn't run very warm so this image is rather exaggerated. I'll explain a bit more later.

So I started off by writing a Python script that runs on my RasPi. It measures the temperature and then logs it to a SQLite3 database that I store in a shared folder on a mounted USB flash drive. I have accelerometer data in the database too, but that will be added a bit later.

That is all that happens on the RasPi. Next I wrote a LabVIEW program that queries the database over the network to get all the data. I need to do a bit of work on my query to just return the last line of data but that I'll add in future versions.

To query the SQLite3 database, I used the this toolkit which works really well and is super simple to get set up. Once I have the temperature, I need to display it on in user interface. This is where Sensor Mapping Express VI comes in really handy.

All you need to do is point to your .stl file and select where you want to the temperature sensors to sit on the RasPi. I used this model which I converted using Google SketchUp. This is where I had to use four dummy senors to be able to show the temperature difference. I have set the outside 4 sensors to 0 degrees Celsius and only sensor 0 is getting the temperature from the database. With more sensors this can be made a lot more accurate. As I said earlier, this is just to prove a concept for now.

Every 100ms I query the database, build an array with the temperature data and then apply it to the Sensor Mapping Express VI. The temperature profile then changes according to the surface temperature of the RasPi.

Here are the colours that I used for my mapping:

Temperature vs Colour mapping:

0 Celsius R-0 G-0 B-255

21.25 Celsius R-0 G-255 B-255

42.5 Celsius R-0 G-255 B-0

63.75 Celsius R-255 G-255 B-0

85 Celsius R-255 G-0 B-0

I have already connected up an ADXL345 accelerometer which is acquiring tilt and pitch values, so my next step is to be able to move the model in LabVIEW as I move my physical RasPi. Should be some fun for a few more hours.

Monday, 22 April 2013

I have been using BottlePy on my Raspberry Pi for quite some time. I really like the simplicity of the framework and the ease at which you can get something up and running. The one issue I had, was that you could not load static css or js files.

There are ways around this, like placing your files in Gist and linking to the raw code, but this can be an issue when you want to run your webserver 'offline'. The documentation is not very clear on how to do this, so here is what I did to get it working properly.

This is the template that I use to route the static files. This is part of my main python code that runs the server.

Then all you need to do is add your file names in the .tpl file. By doing this, your css, or js files can be stored locally so they can still be served if you are offline.

That is about it. I hope this helps because I really find this framework great to use and works flawlessly on my Raspberry Pi.

For a long time now I have been using LabVIEW, but I am not very diligent at using source control. Source control is one of those things that you never really need until it's too late. So this weekend I decided to install TortoiseSVN on my laptop to start out small, but get into the habit of backing up and recording the changes I make to my code.

To get up and running is rather easy. Go over to TortoiseSVN and download the install file. Once installed, you are ready to get going.

The first thing to do is make a folder somewhere to store your repository. I called mine svn_repos. Now right click, you will see an option for TortoiseSVN. Select the Create repository here option from the drop down menu.

Once you have created the repository, go over to the folder that you want to back up. Right click on the folder and select the import option under the TortoiseSVN menu. A window will pop up where you need to enter the path and details of the change. My folder name is TemperatureLogger so just change that in the path to suit your folder.

Press OK and all the files in that folder will be backed up.

Now you need to get a working copy. I use the same folder but you can select any folder for your working copy. Right click on the folder that you have just imported and select the SVN Checkout option. Select your path and if it is the same path you will get a warning. Click OK and when the checkout is complete, you will notice that there is a green tick icon over the folder. When you make any changes to the files, that green icon will turn red.

The LabVIEW part is to now install the JKI Toolkit for TortoiseSVN. Firstly you need to install the VI Package Manager. Once installed, search for TortoiseSVN in the user interface and install it. This takes a couple of minutes and needs your input for a few of the steps.

Once everything is installed, open one of the files that you previously imported and checked out in LabVIEW. Make any change and then save it. You will now notice that there is a red icon over the files that have been changed.

In LabVIEW, go to tools > TortoiseSVN > commit.

Here you will be given the option to add a comment for the changes that were made. This helps you track your changes over time.

You will now notice that icons over the files are back to green letting you know that you have backed up all your files.

You can also get these options directly from Windows Explorer, but it is really convenient to have the option to back up your work directly from LabVIEW. There are many more tools to be used and they are explained pretty well in the documentation.

Well I hope this helps you start to back up and document the changes that are made to your programs. Please don't forget that this can be used for any type of files, not just in LabVIEW. All you need to do is right click on the file or folder and choose the option under the TortoiseSVN menu.

Tuesday, 16 April 2013

This is something I have been wanting to try for quite some time but never really found much info on how to do it. Well I sat down the other day to get it done and realised that it is MUCH easier than I expected.

My objective is to directly connect my Raspberry Pi to my laptop using an ethernet cable. In the next few months I am going to be away from a decent internet connection but I still wanted to do some work on my RasPi. So my Google searching started, finished and here is what to do.

The process uses a built-in feature of Windows 7 called Internet Connection Sharing (ICS). In a nutshell, you can use any Windows computer with more than one network connection, WiFi and LAN, and share the connection to other computers.

Firstly you need to set up the settings on Windows. You need to go to the properties of your disconnected LAN connection and click on the sharing tab. Then check the box to allow other network users to connect through this internet connection.

The tricky thing to set up is the IP address that you are going to give the RasPi. You need to check the TCP/IPv4 settings under the Networking Tab. I picked an IP address and gave my RasPi a static address so that I know what it is when ever I use this connection.

Next you need to power up your Raspberry Pi and connect to it some way. Either use a WiFi connection that is already set up, an ethernet connection to your router or using the serial port on the GPIO.

You then need to set up the IP address by editing the interfaces file.

sudo nano /etc/network/interfaces

Change the part of the file that refers to your eth0 connection to look similar to below. You might have other settings in there like WiFi IP addresses and passwords but just leave those alone.

iface eth0 inet static

address 192.168.137.184

netmask 255.255.255.0

Once you have saved the interfaces file, send the shutdown command so that you can change over the connections. Once powered off, directly connect your RasPi ethernet port to your Windows ethernet port. You should be able to use both straight-through and cross-over cables. Now power up the RasPi.

Once booted up, you should be able to log in with Putty to the static IP address that you set above.

And that is pretty much it. Another cool thing by connecting this way is that you should be able to power your Raspberry Pi from your computer USB port. This makes transport really easy as all you need is an ethernet cable and a USB cable to get up and running.

Hope this helps and if you have comments or questions, please leave them below and I'll get back to you as soon as I can.